Gas turbine machines operate under extremely high temperature ranges and cooling air is frequently used to cool the constituent components of the machine. This becomes particularly important when tactical aircraft must avoid being detected by guided missiles and anti-aircraft artillery. Under heightened and even normal operating conditions, gas turbine exhaust nozzles produce infrared radiation which is not desirable because the enemy can detect such signals and launch an attack using the heat signals that are being generated by the gas turbine engine.
In turbine machines that produce high fan pressure ratios the cooling air is highly compressed which results in elevated temperatures in the exhaust nozzle. This results in insufficient cooling by virtue of the increased air temperature. Bypass air may be directed to the turbine nozzle where substantial pressure is available to direct and modulate cooling flow.
Gas turbine exhaust nozzles can be vectored through a series of mechanisms, called flaps, so as to enhance cooling and performance of the turbine machine. In high performance, thrust augmented engines, there is a high area ratio between the outlet and throat area. Thus, since each engine is usually used in very large, multi-engine aircraft, it is highly desirable that the engines and their exhaust nozzles be clusterable so as to produce minimum base drag.
Exhaust nozzles may have an exterior shell casing of generally circular cross-section and include a number of circumferentially positioned and overlapping flaps which are actuatable between minimum and maximum positions. However, such constructs employ overlapping flap designs that present several limitations in achievable area ratios for the nozzle. Such nozzle configurations have to cope with the varying external geometry, which can be a problem in view of engine clustering and aircraft tail geometry, which may increase base drag due to necessary spacing.
It would be helpful to provide an improved gas turbine vectorable nozzle that improves the performance of the aircraft while employing actuatable flaps to accomplish preferred exit area of variability.